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The Muscular Mink
- CLASS COPY The mink (Mustela vison) has a long slender body,
long busy tail short legs and sharp, powerful teeth.
These characteristics allow minks to be extremely
agile runners, excellent swimmers and efficient
hunters. The minks used for dissection purposes are
typically obtained from commercial mink ranches and
sold for their fur; thus they are already skinned. They
are usually also missing the distal portions of the
forelimbs and hindlimbs, as these regions are
removed during the skinning process. Another caveat
concerning the mink is that commercial dealers keep
most of the females for breeding purposes, As a result, most specimens for dissection are males.
OBJECTIVES:
 Locate and identify selected muscles of the muscular system
 Develop skills in dissection
SET UP:
 Obtain your group’s dissection equipment from the cabinet. Check to make sure all your equipment
is present and cleaned.
 Obtain gloves from the materials station and put on an apron to cover your clothes.
 Take your dissecting tray to the materials station and place one mink in it.
 Rinse the excess preservative fluid out of your specimen’s skin (to save your nose while skinning),
and then pat it with paper towels until it’s only damp.
Procedures:
Use the following guide to complete the dissection of the mink. Actual steps are isolated in boxes and more descriptive
(helpful) information are in the paragraphs. Make sure to read the entire box for directions before actually starting any
activity. When dissecting the muscle, be careful to not destroy the tissue. Use the picture guide provided to assist you in
finding all of the muscles mentioned throughout the dissection.
Remove all of the fat and membranous fascia from the external surface of your mink. The best
strategy for removing this material is to use a blunt probe to tease the tissue away from the
muscles. After all the extraneous tissue is removed and the superficial muscles have been
exposed, lay your mink on its back to view the superficial ventral muscles of the head and neck.
HEAD, NECK, and PECTORAL REGION (VENTRAL ASPECT)
Examine the muscles of the ventral surface of the mink’s neck. The largest and most cranial muscle
of the ventral surface of the head is the MASSETER, the primary muscle involved in chewing. The
masseter stretches from the zygomatic arch of the skull to the masseteric fossa of the mandible.
Ventral to the masseter (on the underside of the neck), locate the MYLOHYOID. This long, thin
muscle runs longitudinally from the medial surface of the mandible to the basihyal (the body of the
hyoid apparatus) where it meets the adjacent mylohyoid (from the other side of the body) at the
midline of the neck. The mylohyoid assists in raising the floor of the mouth.
The DIGASTRIC muscle is located along the medial side of the mylohyoid. It originates from the
paraoccipital and mastoid processes of the skull and inserts on the ventral surface of the mandible.
Its action is antagonistic to that of the masseter; the digastric depresses the mandible.
On the ventral side of the neck, locate the STERNOMASTOID, a rather large muscle extending from
the sternum cranially to its insertion point on the occiput of the skull. This muscle is primarily
responsible for turning the head.
Lateral to the sternomastoid, identify the CLAVOTRAPEZIUS, which extends from the occiput to the
clavicle and the CLAVODELTOID which extends from the clavicle to the humerus. Together these
muscles pull the humerus forward.
Further caudally identify the PECTORALIS MAJOR and the PECTORALIS MINOR. These two large
muscles work in concert to adduct the forelimb of the mink. They both originate on the sternum and
insert on the proximal end of the humerus.
On the ventral surface of the pectoral region, use scissors (or scalpel) to cut through the left side
of the pectoralis major and sternomastiod. Start at the caudal point of the pectoralis major and cut
along the median line towards the cranium. Stop at the sternomastoid and fold the muscles off to
left side.
One major muscle lies underneath the sternomastoid and pectoralis major. Locate the
CLEIDOMASTOID, a long muscle running from the clavicle to the occiput. This is another muscle that
turns the head of the mink. You can also see the pectoralis minor more prominently.
MEDIAL REGION OF THE ARM
Now examine the medial surface of the distal forelimb. Again, starting from the cranial surface of the
forearm, you will see the brachioradialis and the adjacent extensor carpi radialis longus. Adjacent to
these muscles is the extensor carpi radialis brevis, a short muscle originating from the lateral
epicondyle of the humerus and inserting on the 3rd metacarpal. This muscle extends the paw. The
large BICEPS BRACHII is visible on the proximal portion of the forelimb. The smaller pronator teres
is located near the insertion of the biceps brachii. As its name suggests, the pronator teres pronates
the paw. Three major flexor of the wrist and digits can be found on the medial surface of the distal
forelimb. Identify the flexor digitorium profundus, the flexor carpi radialis, and the flexor digitorium
superficialis. These muscles all originate on the humerus and insert onto the metacarpals or
phalanges of the paw.
THE ABDOMEN REGION
Use scissors (or a scalpel) to make very SHALLOW incision through a small portion of the
outermost muscle layer of the abdomen. Make incisions along 3 sides of an imaginary square
about 1 inch across and reflect this “flap” of the muscle back. This will allow you to view both the
superficial and deep musculature of this region. The layers of muscle in this region are bonded
tightly together by fascia and care will be required to separate them completely.
The outermost abdominal muscle layer is composed of the EXTERNAL ABDOMINAL OBLIQUES
which compress the abdomen and help flex the trunk. The muscle fibers of these run diagonally
across the abdomen at an oblique angle to the torso, and their name is derived from this
arrangement. Underneath this layer you will find the INTERNAL ABDOMINAL OBLIQUES. Their
muscle fibers run at a ninety degree angle to those of the external obliques.
The innermost layer of abdominal muscles runs horizontally across the trunk (perpendicular to the
long axis of the body) and is composed of the TRANSVERSUS ABDOMINIS muscles. All three of
these muscles insert on the linea alba, a long, thin white band of connective tissue running down the
midventral line of the abdomen, separating the ventral surface of the mink into left and right halves
and surrounding the RECTUS ABDOMINIS muscle.
PELVIC and MEDIAN REGION of the HINDLIMB
On the medial side of the hindlimb, the most cranial thigh muscle is the SARTORIUS which adducts
the thigh and extends the hindlimb. The largest muscle on the medial side of the thigh is the
GRACILIS which also adducts the thigh. Both muscles insert on the tibia and fascia of the knee, but
the sartorius originates from the ilium, while the gracilis orginates from the pubis and ischium.
On the left hindlimb of your mink, make a transverse incision across the gracilis and the sartorius.
Reflect each flap back to expose the underlying deep musculature of the medial side of the
hindlimb.
Identify the RECTUS FEMORIS, a fairly prominent muscle stretching from the ilium to the tibial crest.
The rectus femoris extends the hindlimb. Now locate the adductor longus and the adductor femoris
muscles. These two muscles originate on the pubis and insert on the femur; they both adduct the
thigh. The SEMIMEMBRANOSUS, is clearly visible from this aspect. Likewise, the
SEMITENDINOSUS is more visible from the medial aspect of the hindlimb. Both of these muscles
extend the hip and flex the hindlimb.
Examine the medial aspect of the distal portion of the right hindlimb of your mink. One of the most
prominent muscles of the distal hindlimb is the calf muscle, or the GASTROCNEMIUS. The
gastrocnemius originates on the femur and inserts on the calcaneus, extending the hindfoot when it
contracts.
Create a FULL PAGE sketch of the ventral aspect of the mink. In the sketch, include all of the
muscles identified above in bold. Make sure to include a descriptive title and to follow proper
labeling guidelines.
HEAD, NECK, and SHOULDER REGION (LATERAL ASPECT)
On the lateral surface of the mink’s head, locate the prominent TEMPORALIS muscle running from
the temporal fossa of the skull to the coronoid process of the mandible. This heavy muscle lifts the
mandible. Caudal to the temporalis is the clavotrapezius (identified earlier) and caudal to the
clavotrapezius is the ACROMIOTRAPEZIUS. This is a large, broad muscle that originates along the
spine and inserts on the scapula. Its role is to adduct and stabilize the scapula.
Near the acromiotrapezius lie two smaller muscles: the SPINODELTOID and the SPINOTRAPEZIUS.
The spinotrapezius is another muscle inserting on the scapula, whereas the spinodeltoid inserts on
the deltoid ridge of the humerus and abducts the humerus. Another large, flat muscle, the
LATISSIMUS DORSI, originates from the dorsal fascia of the thorax and inserts on the medial
surface of the humerus. This broad muscle pulls the humerus backward.
FORELIMB REGION (LATERAL ASPECT)
The triceps muscle (actually a complex of three muscles) is a major component of the proximal
portion of the forelimb in the mink. The TRICEPS LONG HEAD, originating on the scapula, the
TRICEPS LATERAL HEAD, originating on the lateral surface of the humerus, and the TRICEPS
MEDIAL HEAD (not visual superficially), originating on the humerus, all insert by a common tendon
on the olecranon process of the ulna and assist in extending the forearm. The smaller and more
cranial BRACHIALIS originates on the humerus, inserts on the medial surface of the ulna and, along
with the biceps brachii, works antagonistically to flex the forearm.
Seven prominent flexors and extensors are visible on this side of the arm. Starting with the cranial
aspect of the forelimb and moving caudally, first locate the BRACHIORADIALIS muscle which lies
along the cranial border of the humerus and inserts on the styloid process of the radius. This muscle
supinates the paw. Next, identify the extensor carpi radialis longus, the extensor digitorum communis,
the extensor digitorum lateralis and the extensor carpi ulnaris. These four muscles are responsible for
actions that extend either the entire wrist or a few digits of the paw.
PELVIC REGION AND HINDLIMB (LATERAL ASPECT)
On the lateral side of the hindlimb there are six major muscles. The most cranial is the SARTORIUS
(already identied), which stretches from the ilium to the knee and extends the hindlimb and adducts
the thigh. The tensor fascia lata runs from the crest of the ilium and attaches to the front of the knee.
Dorsal to the tensor fascia late, locate the GLUTEUS MAXIMUS, a rather large muscle originating on
both the ilium and sacrum and inserting on the femur. This muscle abducts the thigh.
Another prominent hindlimb muscle that also abducts the thigh (and flexes the hindlimb) is the
BICEPS FEMORIS. This is the largest muscle on the lateral side of the hindlimb and it stretches from
the tuberosity of the ischium to the dorsal border of the tibia and patella. Caudal to the gluteus
maximus is the CAUDOFEMORALIS which abducts and extends the thigh. Finally, identify the
SEMITENDINOSUS, stretching along the caudal border of the hindlimb from the tuberosity of the
ischium to the crest of the tibia.
Make a transverse cut (perpendicular to the fibers) through the gluteus maximus, biceps femoris,
and tensor fasciae latae. Reflect these muscles back to expose the next layer of musculature.
Three major muscles are visible in this middle layer. First identify the GLUTEUS MEDIUS. This
muscle originates from the lateral surface of the ilium, inserts on the greater trochanter of the femur
and abducts the thigh. Next, locate the VASTUS LATERALIS originating on the greater trochanter of
the femur and inserting on the vastus medialis and rectus femoris muscles and patella. The vastus
lateralis extends the hindlimb. Finally, identify the TENUISSIMUS, a thin strip of muscle that extends
from the base of the tail to the lateral surface of the hindlimb. This muscle flexes the hindlimb.
Finally, examine the lateral aspect of the distal portion of the hindlimb of your mink. The most cranial
muscle in this region is the TIBIALIS CRANIALIS, so named because it extends along the cranial
surface of the tibia to its insertion point on the first metatarsal. Its role is to flex the hindfoot.
Create a FULL PAGE sketch of the lateral aspect of the mink. In the sketch, include all of the
muscles identified above in bold. Make sure to include a descriptive title and to follow proper
labeling guidelines.
CLEAN UP!
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Make sure that any removed tissues are placed in a towel and thrown away.
Place the mink in a large plastic bag, fold down, and clip the top.
Discard your gloves in a lined trash can.
Wash, rinse, and thoroughly dry any tools and equipment used before returning your group’s
equipment to the cabinet.
 Wipe down your lab station and return any other used materials to the materials station.
If I find that any of tools are missing from your inventory or clean up is not properly
completed, bevery member of your group will lose 10% of the practical points.